This invention relates to a new and useful method of locating an underground mine fire by measuring the pattern of measured combustion product arrival times at detector locations with a computer-generated array of simulated patterns. Enhanced safety for underground mine workers is a stated policy of the Federal Government. Rapidly determining the location of an underground mine fire has long been a goal of mine ventilation engineers. If the location is known, preferred escape routes can be chosen by miners, rescue teams can concentrate searches in areas where survivors are likely to be found, and fire fighters can select the most efficient route to the fire and the most effective fire fighting strategy. Since the spread of toxic combustion products, and the safety of underground personnel, are greatly influenced and often determined by the mine's ventilation streams, and as a result of research dealing with mine stench fire warning system performance, it was concluded that the analysis of ventilation patterns would provide the most rapid and reliable means for locating the source of contaminant.
The principal disadvantages of the prior art are its inherent slowness, imprecision, and hazard to personnel-the antithesis of an ideal detection system. The only known method of locating a fire in a complex network of underground mine workings is the practice of fire bossing. Fire bossing is the manual inspection of mine workings for signs of fire. The obvious deficiencies of this practice are the time required to survey a mine (some mines comprise hundreds of miles of workings) and the extreme fire, smoke, and toxic gas hazards to the inspectors.
The practice of installing sophisticated electronic fire detection devices at fixed locations in underground mines is growing rapidly. These systems are gaining widespread acceptance as their performance characteristics, and reliability are becoming more well known. Significantly, however, such detection devices are inherently incapable of locating a fire. They are capable only of indicating that a fire exists somewhere in the mine. It is acknowledged that if every branch of a mine network was fitted with a detection device, the location of a fire within the network could be determined. However, as most mines consist of hundreds or even thousands of branches, doing so would be totally impractical. Such fire detection installations typically involve from 1 to 20 detectors, resulting in coverage ratios (number of detectors versus number of network branches) of 1:20 to 1:500. Even under the most favorable conditions, these detectors are capable of indicating only the general area in which a fire is located. Personnel must still be relied upon to manually search miles of working tunnels to find the fire-among the most hazardous of all jobs in mining or any other industry. Also, as this manual search is quite time consuming, and fires tend to grow in size and intensity with time, mine fires often grow to an uncontrollable size before they are found. In the U.S., 78 percent of mine fires discovered within 15 minutes are easily fought and produce little or no damage to mine workings. However, only about 1/3 of all fires are found within 15minutes.
Functional relationship-based alarm methods have been used for controlling a process as well as fire alarm systems as shown in U.S. Pat. No. 4,749,985 to Corsberg, U.S. Pat. No. 4,692,750 to Murakami et al, U.S. Pat. No. 4,427,974 to Sheahan, U.S. Pat. No. 4,622,538 to Whynacht et al and U.S. Pat. No. 4,551,718 to Cookson et al. The patent to Corsberg describes a methodology which utilizes time-ordered sequences to determine the importance of alarms and to perform other diagnostic functions. In this approach, all possible (or likely) alarm activation sequences are identified and modeled. As a given scenario in the process being monitored develops, the alarm sequence is matched to the modeled sequences in attempting to identify the future state of the process is or is likely to be. This approach is generally presented in the form of logic or cause-consequence trees. Unfortunately these logic trees are difficult and expensive to develop and build, are generally inflexible to change, and are not easily maintained over the life of a plant. As a result, the logic tree approach to alarm analysis has been of limited use in real applications.
The present invention is intended to overcome the aforementioned limitations of the prior art by determining the precise network branch in which the fire is located since each fire location is associated with a unique and recognizable pattern of combustion product arrival times at the various detectors. This capability is superior to the prior art of fire bossing and conventional fire detection systems which only specify the general area of a fire.